WHAT DO I KNOW ABOUT SIMPLE MACHINES? (summary)

SIMPLE MACHINES make work easier for us by allowing us to push or pull over increased distances.

In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. Usually the term refers to the six classical simple machines which were defined by Renaissance scientists:

1. LEVER:

A rigid bar that pivots about one point and that is used to move an object at a second point by a force applied at a third. Here we have a clear example:

2. INCLINED PLANE:

An inclined plane is a ramp assists moving object up and down heights. It is a plane surface, set at an angle against a horizontal surface.

3. WEDGE:

The wedge is the active twin of the inclined plane. But unlike the inclined plane, which is stationary, a wedge does useful work by moving.

4. PULLEY:

Sometimes is not easy to lift heavy objects with only one human force. A basic pulley comprises of a wheel on a fixed axle, with a groove along the edges to guide a rope.

5. WHEEL AND AXLE:

When we have to move a really heavy object, we have to use a great deal of force push it. That's because of:
Friction: force resisting the motion of the object on the ground.
Gravitational force: force that pulls the object to the ground.
The wheel and the axle solves this problem!!!
In this simple machine, a wheel is locked to a central axle and they rotate each other when a force is applied on either one of them.

6. SCREW:

A screw is one of the most commonly used machines in the world. It is a machine that converts rotational motion into linear motion.

Could we live without machines? No. Something as simple as a cart requires wheels to move. Think about how our clothes are cleaned, what do we use to cook food, and how do we get to school on rainy days. It would be very hard to live without machines.

CAMS AND ECCENTRICS are mechanisms that convert rotational motion into reciprocating linear motion. They consist of a revolving piece, the cam or eccentric to give it is proper name, and an element that this piece comes into contact with; the follower or lever. Eccentrics are circular in shape, with the special characteristic that the turning axis is not in the centre. Cams can have any profiles depending on the type of movement that you want the lever to have. In the animations below you can see how they work.

GEARS: Gear trains transmit rotary motion. Gears are toothed wheels that interlock. A gear train is where two or more gears are linked together.

 The driver, turned by hand or a motor, turns the driven gear. Both will automatically turn in different directions. If the driver turns clockwise, the driven will turn anticlockwise and vice versa.

If you use a third gear, it is named idler, the driver and the driven will both turn in the same direction, and the idler in the other directoin. Example: in the photo.






As you can see in the image, the gears are different in size, and this means that they turn in different speeds. In the photo the driver (that is the big gear) makes 1 turn while the driven (the small gear) turns 2 times

Gears can change the type of motion or the direction of motion:
For example you can change from the rotary motion to linear motion.
A rack and pinion are used to turn rotary motion to linear motion. The pinion, a round gear, is turned to move a flat gear, the rack.

A worm drive and worm wheel change the direction of rotation through 90º. The worm drive (the driver) only has one tooth and will turn much faster than the worm wheel, which has many teeth so will turn very slowly.
Bevel gears algo change the direction of rotation through 90º. The teeth are angled at 45º so the gears fit together at right angles.

MECHANICAL SYSTEMS:

Electrical systems aren't the only type of system. There are also mechanical systems. All mechanical systems have mechanisms which transform an input motion into an output motion.

They're designed so you can gain an advantage from using them- they making something easier to do.

Some mechanisms change one type of motion into another.

Linear motion

reciprocating motion

oscillating motion

rotary motion

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